--- a/src/NuMagSANS.cu
+++ b/src/NuMagSANS.cu
@@ -15,0 +16,5 @@ int main(int argc, char* argv[]){
+	if(argc != 2){
+		cerr << "Usage: NuMagSANS <input-file>" << endl;
+		return 1;
+	}
+